text: // MIT License
  
  // Copyright (c) 2019 Erin Catto
  
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  
  // The above copyright notice and this permission notice shall be included in all
  // copies or substantial portions of the Software.
  
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  // SOFTWARE.
  
  #ifndef B2_SHAPE_H
  #define B2_SHAPE_H
  
  #include "b2_api.h"
  #include "b2_math.h"
  #include "b2_collision.h"
  
  class b2BlockAllocator;
  
  /// This holds the mass data computed for a shape.
  struct B2_API b2MassData
  {
  	/// The mass of the shape, usually in kilograms.
  	float mass;
  
  	/// The position of the shape's centroid relative to the shape's origin.
  	b2Vec2 center;
  
  	/// The rotational inertia of the shape about the local origin.
  	float I;
  };
  
  /// A shape is used for collision detection. You can create a shape however you like.
  /// Shapes used for simulation in b2World are created automatically when a b2Fixture
  /// is created. Shapes may encapsulate a one or more child shapes.
  class B2_API b2Shape
  {
  public:
  
  	enum Type
  	{
  		e_circle = 0,
  		e_edge = 1,
  		e_polygon = 2,
  		e_chain = 3,
  		e_typeCount = 4
  	};
  
  	virtual ~b2Shape() {}
  
  	/// Clone the concrete shape using the provided allocator.
  	virtual b2Shape* Clone(b2BlockAllocator* allocator) const = 0;
  
  	/// Get the type of this shape. You can use this to down cast to the concrete shape.
  	/// @return the shape type.
  	Type GetType() const;
  	
  	/// Test a point for containment in this shape. This only works for convex shapes.
  	/// @param xf the shape world transform.
  	/// @param p a point in world coordinates.
  	virtual bool TestPoint(const b2Transform& xf, const b2Vec2& p) const = 0;
  
  	/// Compute the distance from the current shape to the specified point. This only works for convex shapes.
  	/// @param xf the shape world transform.
  	/// @param p a point in world coordinates.
  	/// @param distance returns the distance from the current shape.
  	/// @param normal returns the direction in which the distance increases.
  	virtual void ComputeDistance(const b2Transform& xf, const b2Vec2& p, float32* distance, b2Vec2* normal) const= 0;
  
  	/// Cast a ray against a child shape.
  	/// @param output the ray-cast results.
  	/// @param input the ray-cast input parameters.
  	/// @param transform the transform to be applied to the shape.
  	/// @param childIndex the child shape index
  	virtual bool RayCast(b2RayCastOutput* output, const b2RayCastInput& input,
  						const b2Transform& transform) const = 0;
  
  	/// Given a transform, compute the associated axis aligned bounding box for a child shape.
  	/// @param aabb returns the axis aligned box.
  	/// @param xf the world transform of the shape.
  	/// @param childIndex the child shape
  	virtual void ComputeAABB(b2AABB* aabb, const b2Transform& xf) const = 0;
  
  	/// Compute the mass properties of this shape using its dimensions and density.
  	/// The inertia tensor is computed about the local origin.
  	/// @param massData returns the mass data for this shape.
  	/// @param density the density in kilograms per meter squared.
  	virtual void ComputeMass(b2MassData* massData, float density) const = 0;
  
  	Type m_type;
  
  	/// Radius of a shape. For polygonal shapes this must be b2_polygonRadius. There is no support for
  	/// making rounded polygons.
  	float m_radius;
  };
  
  inline b2Shape::Type b2Shape::GetType() const
  {
  	return m_type;
  }
  
  #endif
  